A rail vehicle consist generally includes two or more rail vehicles that are mechanically coupled together to travel along a set of rails. A train is one example of such a rail vehicle consist. Typically, the train may include one or more powered locomotives and one or more non-powered rail cars. For example, a rail vehicle consist may include a master or lead locomotive, one or more trailing locomotives linked behind the lead locomotive, and one or more non-powered rail cars linked behind the one or more trailing locomotive. The number and type of rail vehicles may differ from this example.
The lead locomotive typically has a power source installed thereon, for example, a diesel engine for generating driving power to propel the locomotive along the rails. In some cases, the trailing locomotives may also have power sources installed thereon.
An operator is generally seated in the lead locomotive for operating the consist. The operator must be able to obtain data, such as throttle level and tractive effort level, associated not only with the lead locomotive but also the trailing locomotives, and to operate certain systems not only in the lead locomotive but also in the trailing locomotives.
For this reason, the lead locomotive and the one or more trailing locomotives may communicate with each other via a data communication system. The data commination system may be a hardwired multi-unit (MU) cable or, in more modern consists, an interconsist communication (ICC) system such as that described in co-owned United States Patent Publication Nos. 2014/0252174 and 2016/0159379.
Each locomotive also is equipped with multiple axles, a typical number being six. Each axle drives a set of wheels and is itself be driven by an electronically controlled traction motor. However, such wheels may slip when engaged on the rails of a given track. Since wheel slippage reduces fuel efficiency, it is important to optimize the adhesion between each wheel and the rails.
Wheel adhesion is a function of the coefficient of friction and a locomotive adhesion variable. Wheel adhesion is used to determine the tractive effort of each locomotive, or the force generated by the locomotive's engine or motor to move the consist. The more tractive effort a locomotive can produce, the fewer locomotives that are needed to run freight. Creating even a couple percent more tractive effort is a worthwhile objective.
The above need for improved wheel adhesion is even more acute when understanding that the operator controls the locomotive engine speed via a throttle which typically can be set to a discrete number of levels (typically numbered zero through eight) via mechanical notches. To increase the speed of a train gradually, the operator may move the throttle one notch at a time, sending a signal to the controller to increase engine speed by only that defined amount. When a train is operating in the middle throttle notches, increasing wheel adhesion can enable the locomotives to be run at a lower throttle notch and therefore save fuel and reduce emissions.
Thus the present disclosure is directed to a system and method of improving locomotive wheel adhesion and thus tractive effort in a multi-locomotive consist.